Leno nears end of Tonight Show’

An appraisal of a veteran talk-show host and comedian should have lots to say about his funniness.

Let’s just credit Jay Leno with persistence.

Tomorrow night, Leno surrenders his job as host of NBC’s “Tonight Show” after 17 years. It’s a job he won against stiff competition. Then, early in his run, it’s a job he defended against NBC bosses who were having second thoughts.

Since the mid-1990s, he has won the late-night ratings war. With a smile on his face and never a complaint, he has worked tirelessly. (No one could believe it when he took a couple of sick days recently, his first while at “Tonight.”)

And even now, with Conan O’Brien set to take over Monday (thanks to NBC’s transition plan that made Leno a late-night lame duck five years ago), he isn’t really leaving. He’s moving up. Next fall, “The Jay Leno Show” will premiere on NBC weeknights at 10.

At age 59, Leno is graduating from late night to what used to be perceived as TV’s big time. NBC has made him lord of nearly one-fourth of its crumbling prime-time manor.

But as his “Tonight Show” tenure comes to an end, what is his mark on that hallowed institution?

Uhhhhh, what to say, what to say?

It’s so much easier to speak about the three hosts who preceded him.

Steve Allen (1954-57) gets credit for no less than inventing late night, down to the desk and couch. Allen was bespectacled and brainy, with a mischievous wit that would be felt in late-night long after he was gone.

Jack Paar (1957-62) was impishly well-spoken, boundlessly inquisitive and urbane in unpredictable ways — he could blow his top or shed sentimental tears, and still seem suave.

Johnny Carson (the king of Late Night, whose reign began in 1962) put America to bed for 30 years. The things he joked about in his monologue; the guests he welcomed to his couch — he was a major cultural arbiter, a unifying force. America slept better after watching him.

Since May 25, 1992, Jay Leno has sat at the desk.

Make no mistake, he has been a sturdy placeholder. Big chin, unfailingly likable. The sort of regular guy with whom his audience identifies.

And with whom his guests feel peace of mind, knowing Jay will handle them with care.

Jay handles everyone with care — most of all, his 5 million viewers.

Consider how he cares for them in every monologue. He delivers each joke as if for slow learners, with its punch line underlined, reiterated, explained. His policy is clear: No Viewer Left Behind.

Without fail, Leno’s show fills an hour and kills an hour. It never challenges its viewers by daring to do more. It’s stable and dependable, with nothing left to chance or the viewer’s imagination. No danger of a comedy breakthrough here.

Small wonder David Letterman, not Leno, has always been the spiritual successor to Johnny Carson. As Leno’s rival over on CBS, Letterman hosts “Late Show” with the mastery befitting a post-Carson “Tonight.”

He will continue to do so, just as he has for nearly 16 years. No torch is being passed while Dave’s on duty. At NBC, what’s happening is musical chairs.

As of next week, “Tonight” will star Conan, while Jay gets ready for prime time.

“We can hope that Jay expands his audience from 11:30,” said NBC boss Ben Silverman recently, citing prime time’s larger pool of available viewers. “But we’d be happy even at the same rate.”

A late-night talk show sprawled across prime time: It’s a bold plan. Also a fascinating exercise in lowered expectations, with Leno the right man to give it a shot. After all, for 17 years in late night he has vigorously played a game of lowered expectations, and met them.